A common task of audio signal processing is a combining of a multitude of audio sources into a lesser number of channels as dictated by the format of the target final product. To assist the recording engineer with this task, two types of computer based automation systems have been developed which can memorize and recreate any and all of the operator's prior manipulation of the controls.
All systems encode and store position changes of the input devices. Some systems, referred to as "moving fader" systems, can replicate the original motions of the input devices by means of motor driven servo mechanisms with the input device. The replicated movements of the input devices also serve as displays of the current values of the stored information. The majority of these systems also include the audio control element within the servoed input device.
In contrast, the non-motorized automation systems must provide additional devices to display the current values of stored information and to control the audio signal level. The control element in non-servo systems must be independent from the input device so that control changes can occur during replay without any attendant motion of the input device.
Although automation systems have been commercially available, the marketplace demands continued improvements and responsiveness, ease of use and flexibility. A key factor in providing these improvements is the amount of processor time required to quickly respond to system tasks. A common solution is to use multiple general purpose processors to share the workload. A disadvantage and limitation of this approach is that the numerous repetitious instruction fetch cycles required to continuously scan the input/output devices and the communications required between the multiple processors cause a substantial overhead burden which degrade system speed.